SOME FACTORS DETERMINING WATER-TABLE HEIGHTS IN DRAINED HOMOGENEOUS SOILS

Summary The effect of the depth of impermeable floor below the drain level on water table heights in homogeneous soils, drained by a uniform system of ideal drains, for steady state conditions with various rainfall intensities, was investigated by means of hydraulic model and electric analogue experiments. Agreement was obtained between the two series of experiments which indicated that, for a given ratio of rainfall intensity to hydraulic conductivity, the water-table height midway between the drains decreased as the depth of the impermeable floor below the drain was increased from zero, tending towards a constant height when the ratio of the depth of the impermeable floor below the axis of the drain tube to the half spacing of the drains approached 0.3. In addition, in the experiments with a deep impermeable floor, agreement was found with the analytically obtainable solution of the problem with an infinitely deep floor. Water-table heights observed in the non-steady state hydraulic experiments approximated to those of the steady state with uniform distributions of flux cutting the water table for corresponding equal mean distributions, calculated from the drain discharge.